迁移问题

db/migrate/20160108021447_change_attachment_history.rb

@@ -1,9 +1,9 @@
 class ChangeAttachmentHistory < ActiveRecord::Migration
   def up
-    attachments = Attachment.where("container_type =?", "Version")
-    attachments.each do |am|
-      am.update_attribute(:container_type, "Project") unless am.nil?
-    end
+    # attachments = Attachment.where("container_type =?", "Version")
+    # attachments.each do |am|
+    #   am.update_attribute(:container_type, "Project") unless am.nil?
+    # end
   end
 
   def down